Effect of Rearing Temperature and Humidity on Fecundity and Fertility of Silkworm, Bombyx mori L. (Lepidoptera: Bombycidae)

The effect of temperature and humidity fluctuations on fecundity and fertility of the silkworm lines was investigated during autumn and spring by exposing 4 and 5 instar larvae of eleven inbred silkworm lines ( M101, M-103, M-104, M-107, Pak-1, Pak-2, Pak-3, Pak-4, PFI-1, PFI-2 and S-1) to 25±1°C, 30±1°C and 35±1°C in combination with 55, 65 and 75% relative humidity (RH) for 3hr daily. Temperature and relative humidity during larval rearing affected the fecundity and fertility of inbred silkworm lines adversely. The maximum average number of eggs were laid at 25±1°C with 75±5% RH (413.1) followed by 25±1°C with 75% RH (400.4) and 25±1°C with 65% RH (390.9). Significant difference in egg fertility was observed between all the treatments. Maximum average fertilized eggs were recorded at 25±1°C with 75±5% RH (88.77) followed by 25±1°C with 75% RH (86.88) and 25±1°C with 65% RH (85.09) while lowest fertility was shown by 35±1°C with 55% RH (67.52). The deleterious effect of temperature and humidity was observed on fecundity and fertility of inbred silkworm lines. Pak-4 was the best performer with maximum eggs (471.5) at 25±1°C with 75±5% RH followed by PFI-1 (465.2) and M-101(464.1) in the same environment. The best temperature and humidity for rearing silkworm lines for seed cocoon production (to obtain higher number of eggs per moth with increased fertility) is 25±1°C with 75±5% RH. Pak-2, Pak-4, Pak-3 and PFI-I were the better lines which may be utilized in seed cocoon production and hybridization. Investigations elucidated that temperature and humidity variations during larval rearing resulted in low fecundity and high incidence of unfertilized eggs. The study suggests that fecundity and egg fertility can be enhanced by avoiding temperature and humidity fluctuations during larval rearing.